【作者】 徐忠国； 蒋文燕； 陈文革；

【Author】 Zhongguo Xu;Wenyan Jiang;Wenge Chen;School of Biological and Chemistry Engineering /School of Light Industry,Zhejiang University of Science and Technology;

【机构】 浙江科技学院生化/轻工学院；

【摘要】 彩色数字图像输出到承印物以后,呈色域从RGB颜色空间转换至CMYK颜色空间,由此产生了印品与电子原稿的色差。针对采用何种方式映射及对应修正的误差范围,实验将原稿RGB模式通过可感知、饱和度、相对比色、绝对比色等意图转换为配置文件,得到4个CMYK模式。实验在ps软件的Lab模式中,选取映射后的各色块Lab值分别为坐标中心,建立Lab三维坐标系,其中a为x轴,b为y轴,L为z轴。由于设备的限制,试验采用ps软件绘制ab、aL、bL三个色域图来确定各色块的空间宽容域。根据颜色对比现象,背景采用中心色块的颜色,与其他色块产生颜色对比,易于人眼察觉。计算色差公式,在Lab空间中画出色差球、彩度差圆柱面及色调差抛物柱面,参照标准色调差表示出特定条件的范围,在Lab色彩空间绘制颜色容差。计算不同映射的容差范围,对最合适的映射模式输出印品,对计算机和海德堡印刷机进行ICC色彩管理,通过CTP设备进行制版,最后采用海德堡胶印机输出样张。为保证数据的可靠性,实验分别选用了哑粉纸、铜版纸、胶版纸等不同类型的承印物。建立印品色块的Lab值与对应容差的关系,求出对应修正的误差范围。将以上的数值关系反馈于色域转换和图像复制的过程,对印刷工艺进行优化,然后再次进行颜色的测量和计算,验证色域转换的精度。更多还原

【Abstract】 When color digital images output on substrates,color space is converted,causing the color differences between prints and electronic manuscript.In order to locate which way to map and relatively corrected error range,the original is converted to 4 CMYK modes through the intentions of perception,saturation,relative colorimetry and absolute colorimetry respectively.Photoshop software is used to draw a-b,a-L and b-L color gamut graphs to determine the spatial domain of each color tolerance.The background is center color contrasting with the other color.Thus,the graphs can be straightly detected by human eyes easily.In complex calculation of formula,experiment successfully draws color difference ball,chroma difference cylinder and hue difference parabolic in Lab space.It really helps figure out the tolerance range of different mappings and prints.The above numerical relationship is fed back to the process of color gamut conversion and image reproduction.Then color measurement and calculation are further conducted to verify the accuracy of color gamut conversion.更多还原